This invention relates to signature handling and, more particularly, to apparatus and a method for transforming a stack of signatures into a moving stream of individually arranged signatures for collating purposes.
In the manufacture of books, as the individual signatures comprising the book leave the printing press, they are collated in a signature gathering machine preparatory to binding. A gathering machine has hoppers in which the signatures are stacked on top of each other and gripping fingers that pull the signatures one at a time in turn from the bottom of the stack so each signature can be collated with the other signatures comprising the book One station of a typical gathering machine is disclosed in Hageman et al U.S. Pat. No. 3,650,525, which issued on Mar. 21, 1972. Hageman et al disclose a rotary drum mechanism with suction detacher means and carrying grippers. With each revolution of the rotary drum mechanism, the suction detacher means and carrying grippers remove one signature from the bottom of the stack.
If many signatures are stacked in the hopper of a gathering machine, the weight bearing on the bottom signature is too great to permit its removal from the stack. Therefore, the height of the stack of signatures in the hopper must be closely controlled. When signatures are manually loaded into the hoppers, the loading operation requires constant and close attention by the attendants to insure that the hopper does not become empty or too full. Generally, the loading operation requires at least one attendant for every three hoppers, which represents a substantial labor expense in a book manufacturing operation.
Knopp U.S. Pat. No. 3,945,633, which issued Mar. 23, 1976, discloses a hopper loading machine. The signatures are manually loaded onto a horizontal conveyor on edge. These signatures are fed by the horizontal conveyor to an inclined conveyor, which carries the signatures in a shingled stream to the top of a hopper for a gathering machine. The signatures are automatically fed to the hopper to control the height of the signatures therein. Many more signatures can be loaded on edge onto a horizontal conveyor than can be loaded in the hopper on top of each other, and therefore, less operator attention is required. The described hopper loader does not work effectively on 1/4 fold signatures having a paper weight of 22.5 pounds or less, such as telephone book paper. Moreover, the maximum feed rate is about 120 signatures per minute and the signatures are not delivered in synchronism with the pin chain of the gathering machine.
Mueller Martini AG, a Swiss company, offers for sale a gathering machine in which a stack of signatures on edge is fed to a rotary drum mechanism of the type disclosed in the above-mentioned Hageman et al patent. As a result, the signatures in the stack are fed by vacuum suckers and grippers of the rotary drum mechanism to the gathering track one at a time in synchronism with the pin chain. Under some conditions, this gathering machine experiences many missed signatures, i.e., the rotary drum mechanism fails to pick up a signature with each rotation. As a result, many rejects are produced during book manufacture.